Machines for conveying particulate or granular material using a vacuum are well known, for example for use in conveying grain. These machines allow pickup of granular material with a flexible hose that allows considerable freedom of movement. A fan or air pump is used to establish a flow of air from the intake end of the hose through the machine to a discharge. An intake nozzle at the end of the hose is placed in the granular material, and the air being sucked into the intake end carries picks up granular material and establishes a stream of mixed air and granular material that is carried through the hose. Typically the hose is in turn attached to a rigid tube, with the tube and hose forming an intake conduit between the vacuum conveyor and the intake nozzle. Sections of tube are added or removed, depending on the distance between the vacuum conveyor and the granular material.
When the intake end of the nozzle is placed into a pile of granular material, the flow of air is substantially blocked, and so a vent is provided on the intake nozzle so that air can enter the nozzle and maintain the flow of granular material. Such vents typically comprise one or more slots cut into the wall of the nozzle, although numerous variants are known. Typically a baffle is also provided to vary the area of the vent that is open, and so allow an operator to regulate the flow of air in through the vents in accordance with the particular material being conveyed, the length of the intake conduit between the vacuum conveyor and the intake nozzle, and other like operating conditions.